This application claims priority under 35 USC 119 of Japanese Patent Application Nos. 2000-169170, 2000-357409 and 2000-212373 filed in JPO on Jun. 6, 2000, Nov. 24, 2000 and Jul. 13, 2000 respectively, the entire disclosures of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an image scanning apparatus that can read both front and back sides of each of sheets successively fed to a scanner part.
2. Description of the Related Art
When a conventional image scanning apparatus scans both sides of an original document, its scanner part first scans a front side. The original document is then transferred in a paper path to a space above a discharged paper receiving tray (first paper path) by discharge rollers, and the discharge rollers that nip an end of the original document are caused to rotate in a reverse direction so that the document is moved backward and introduced into another paper path (second paper path) to turn the document upside down. After that, the document is sent to the scanner part again such that a back side of the document is scanned. Subsequent to this, the document is discharged into the discharge tray.
After reversing the document feed direction in the conventional image scanning apparatus, the document is transferred into the second paper path, as mentioned above. For this reason, a guide member is generally disposed at a branching point between the first and second paper paths. The guide member is a switching member to determine which paper path should be used.
The original document is discharged on the discharge tray with its front side being up. In other words, the first page is up and the second page down. Therefore, when two original sheets of paper are discharged on the tray, page 1 (front side of the first sheet) faces page 4 (back side of the second sheet).
In order to overcome this problem, the original sheet is reintroduced into the paper path after both the two sides of the original sheet are scanned, so that the original sheet is turned upside down again. In this case, however, no scanning is performed. The original paper is then discharged onto the discharge tray.
As a result, page 1 is down, page 2 is up, page 3 is down (so that it contacts page 2), and page 4 is up (in case of the two-sheet scanning).
In this conventional arrangement, however, the original document has to pass the scanning part three times, i.e., when its front side is scanned, back side is scanned and the document is turned upside down without scanning. Accordingly, the scanning operation takes a relatively long period as a whole.
Further, when the original paper passes over the scan part for the third time, no scanning operation is conducted. During this action, therefore, the scanner part is occupied by the original paper without scanning operation, and it is not possible to feed the next original paper to the scan part. Accordingly, the scanning speed of the machine is lowered as a whole.
Moreover, the guide member located at the branching point between the first and second paper paths is driven by an electrically controlled element such as a solenoid when it is switched to connect the first or second paper path to the paper discharge exit. It is required to synthesize rotating movements of paper feed roller(s) with the switching movement of the guide member. This makes the paper feed control complicated.
An object of the present invention is to provide an image scanning apparatus that can eliminate the above-described problems.
One concrete object of the present invention is to reduce the time needed to scan both sides of an original document.
Another concrete object of the present invention is to drive a guide member disposed at a paper path branching point without employing a complicated control program.
According to one aspect of the present invention, there is provided an image scanning apparatus comprising: a scanner; a document feeder for receiving sheets in a stack and feeding one sheet at a time; an inverting path for turning a sheet, which is fed from the document feeder, upside down before scanning; a transportation means located at a downstream end of the inverting path for reversing a transportation direction of the sheet and feeding the sheet to the scanner through a return path; a reversing means for reversing the transportation direction of the sheet after the scanner scans one side of the sheet, and feeding the sheet to the scanner again to scan the other side of the sheet; and a discharging means for discharging the sheet after the two sides of the sheet are scanned. The sheet is substantially turned upside down when its transportation direction is reversed and fed to the scanner for the second time.
A guide member may be located a bifurcation of the return path and the inverting path for opening one of the return and inverting paths and closing the other of the return and inverting paths, whereby it is possible to introduce the sheet into the return path after the sheet is fed towards the scanner from the downstream end of the inverting path.
The transportation means may include at least one roller, and the reversing means may include at least one roller. The guide member may pivot as the transportation means rotates. The guide member may be operatively connected to the transportation means via a torque limiter.
Three rollers may be arranged to form two pairs of rollers, and one of the two pairs of rollers may constitute the transportation means whereas the other pair of rollers may constitute the reversing means. The latter pair of rollers may also constitute the discharging means.
Alternatively, two rollers may only be arranged to constitute all of the transportation means, reversing means and discharging means.
Additional objects, aspects, benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention pertains from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings.